A 45 year-old male presents with right thumb pain and deformity after falling off his bicycle. You obtain hand x-rays and see the following images. What is the most likely diagnosis, differential diagnosis, and management plan?
- Dislocation of the first carpometacarpal (CMC) joint.
- Pearl: CMC dislocations account for less than 1% of all hand injuries [1,2]. Isolated dislocations are even more uncommon, and are usually associated with Bennett, Rolando, and carpal fractures [1-4]. The majority of dislocations are dorsal [2,4]. Misdiagnosis or delayed treatment may result in joint instability, early degeneration of the articular cartilage, and decreased grip strength [1-5].
- Bonus: There are two other interesting findings on this radiograph. First, there is a well corticated osseous fragment at the base of the second proximal phalanx that is likely a chronic fracture deformity. Second, there is a metallic foreign body between the third and fourth metacarpal heads that is possibly a BB gun pellet.
- Thumb CMC dislocations are often caused by axial loading of the thumb in a flexed position, and less commonly, direct force into the webspace between the first and second digits [1-4].
- Exam findings include painful and limited range of motion of the thumb and often subtle deformity and swelling over the dorsoradial side of the hand [1,4].
- Plain radiographs should be taken of the hand with AP, lateral, and oblique views [1-3]. Stress views and CT scan may also be helpful to identify other injuries, as thumb CMC dislocations are rarely isolated [1,2].
- The CMC dislocation should be anesthetized with an intra-articular injection, and then closed reduction should be performed with traction [1,4].
- Immobilize the joint with a thumb spica splint with the first metacarpal held in abduction and extension with the wrist in pronation. Closed reduction is often unstable [1-6].
- The patient should have follow-up arranged with a Hand Specialist within 3-4 days [1,7].
Figure 2. Post-reduction XR that showed interval reduction of the first CMC joint with normal alignment. Author’s own images.
- Orthopedics should be immediately consulted for a thumb CMC dislocation if there is an open fracture-dislocation, neurovascular compromise, or irreducible dislocation.
- There is debate over the optimal treatment strategy, and several studies have compared nonoperative and operative treatment .
- Nonoperative management: immobilization in a short arm thumb spica cast for 4-6 weeks .
- Operative treatment: closed reduction and percutaneous fixation with Kirschner wires for 5-6 weeks [3-7].
- Patients who experience persistent instability may require ligamentous reconstruction [3-5].
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- Atkinson R. Hand. DeLee & Drez’s Orthopaedic Sports Medicine: Principles and Practice. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2009: 1386-1398.
- Fotiadis E, Svarnas T, Lyrtzis C, Papadopoulos A, Akritopoulos P, Chalidis B. Isolated Thumb Carpometacarpal Joint Dislocation: A Case Report and Review of the Literature. J Orthop Surg Res. 2010;5(16):1-5. PMID: 20219137
- Mailhot T, Lyn ET. Hand. Rosen’s Emergency Medicine Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014: 555-556.
- Horn AE, Ufberg JW. Management of Common Dislocations. Roberts & Hedges’ Clinical Procedures in Emergency Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2014: 981-984.
- Raukar NP, Raukar GJ, Savitt DL. Extremity Trauma. The Atlas of Emergency Medicine. 4th ed. New York, NY: McGraw-Hill; 2016: 298-300.